This invention relates generally to surface mounting technology utilized to electrically and physically interconnect electronic components.
In surface mount technology (SMT), two surfaces may be electrically interconnected using solder bumps or balls that are deposited upon one of the surfaces and then reflowed or heated to solder the two surfaces together. SMT may be an advantageous process because it is not necessary to work in the region between the two surfaces to be joined and because a large number of components may be connected in the same reflow step.
A problem may arise, however, when one of the surfaces to be bonded is irregular. For example, one surface to be surface mounted to another surface may be warped. When the surface mount bumps of uniform size are deposited, an open or poor connection may result. Conversely, if the warp of one surface extends toward the other, solder balls in the intervening area may be excessively deformed causing them to squeeze out and short other electrical components.
Referring to FIG. 6, a first relatively flat substrate 10 may be surface mounted to an irregular substrate 12. In this case, the substrate 12 is warped for illustration purposes. The solder bumps or balls 14 may be applied to the flat surface 12. However, when the two surfaces 10 and 12 are brought together, some of the solder balls may not make effective contact with the surface 12 because of its curvature, while other balls may be excessively deformed raising the possibility of shorts to adjacent components.
Thus, there is a need for a way to deal with the possibility that the spacing between two surfaces to be surface mounted may not be uniform and regular throughout.